Systems and methods for forming refractory metal oxide layers

ABSTRACT

A method of forming (and apparatus for forming) refractory metal oxide layers, such as tantalum pentoxide layers, on substrates by using vapor deposition processes with refractory metal precursor compounds and ethers.

FELD OF THE INVENTION

This invention relates to method of forming a refractory metal(preferably, tantalum) oxide layer, and particularly to a method offorming a tantalum pentoxide layer, on a substrate using a reactivedeposition process with a refractory metal precursor compound with anether.

BACKGROUND OF THE INVENTION

In integrated circuit manufacturing, microelectronic devices such ascapacitors are the basic energy storage devices in random access memorydevices, such as dynamic random access memory (DRAM) devices, staticrandom access memory (SRAM) devices, and ferroelectric memory (FERAM)devices. Capacitors typically consist of two conductors, such asparallel metal or polysilicon plates, which act as the electrodes (i.e.,the storage node electrode and the cell plate capacitor electrode),insulated from each other by a layer of dielectric material.

The continuous shrinkage of microelectronic devices over the years hasled to a situation where the materials traditionally used in integratedcircuit technology are approaching their performance limits. Silicon(i.e., doped polysilicon) has generally been the substrate of choice,and silicon dioxide (SiO₂) has frequently been used as the dielectricmaterial to construct microelectronic devices. However, when the SiO₂layer is thinned to about 10 Å (i.e., a thickness of only 4 or 5molecules), as is desired in the newest micro devices, the dielectriclayer no longer effectively performs effectively as an insulator due tothe tunneling current running through it. This SiO₂ thin layerdeficiency has lead to a

search for improved dielectric materials.

Refractory metal oxides such as tantalum pentoxide (Ta₂O₅), titaniumdioxide (TiO₂), zirconium dioxide (ZrO₂), and hafnium dioxide (HfO₂),are some of the most promising SiO₂ replacements for future DRAM devicessince they meet the requirements for large scale processing andfabrication using conventional microelectronics processing equipment.Furthermore, these oxides have excellent step coverage, and they exhibitcomparatively low leakage current. Ta₂O₅ is of particular interest aslayers of amorphous Ta₂O₅ have a dielectric constant of about 25. Ta₂O₅layers can be formed using chemical vapor deposition (CVD) processes.For example, reacting vapors of Ta(OC₂H₅)₅ (pentaethoxy-tantalum) withoxygen or by reacting vapors of TaF₅ with an O₂/H₂ plasma can formTa₂O₅.

Annealing can improve the crystallinity and resulting dielectricconstant of refractory metal oxide layers. For example, the dielectricconstant of an amorphous Ta₂O₅ layer can be increased to at least 40 byannealing the deposited layer at temperatures over 700° C., causing achange in crystallinity from an amorphous state to what is believed tobe a preferred (001) orientation of a crystalline hexagonal phase ofTa₂O₅. Unfortunately, this increase in dielectric constant of annealedcrystalline Ta₂O₅ layers is counterbalanced by higher leakage currentsthrough the crystal boundaries. High temperature annealing of a Ta₂O₅layer on polysilicon also inevitably produces a thin SiO₂ interfaciallayer between the Ta₂O₅ layer and the polysilicon due to ambientoxidation during the deposition process and during any post-processingsuch as annealing. This SiO₂ layer insures better interfacial propertiesbut also causes a reduction of the global dielectric constant of theTa₂O₅ capacitor. A metal nitride barrier layer can be applied to thepolysilicon substrate prior to formation of the Ta₂O₅ layer to avoidformation of the SiO₂ interfacial layer but at the cost of addinganother processing step. Metal nitride barrier layers are also likely tobe oxidized by high temperature anneal processes.

Changing the nature of the substrate and curing conditions during CVDprocessing can improve the dielectric constant of resulting Ta₂O₅layers. For example, Kishiro et al., “Structure and ElectricalProperties of Thin Deposited on Metal Electrodes,” Jpn. J. Appl. Phys.,37:1336-1338 (1998) report crystalline Ta₂O₅ layers having dielectricconstants over 50 made by depositing the layers on platinum andruthenium substrates rather than on poly-Si electrodes and annealing at750° C. For another example, Lin et al., “Ta₂O₅ thin films withexceptionally high dielectric constant,” Applied Physics Newsletter,74(16):2370-2372 (1999) report that if a Ta₂O₅ layer is deposited on aRu/TiN/Ti/SiO₂ layered substrate, its dielectric constant can beincreased up to 90-110 after N₂O plasma treatment and then rapid thermalnitridation (RTN) at 800° C.

To date, efforts to improve the dielectric constant of Ta₂O₅ layers haveeither required high temperature processing that has led to variouslayer deficiencies or have required specialized processing or substrateconsiderations. Thus, there remains a need for a vapor depositionprocess to form Ta₂O₅ layers that have high dielectric constants and lowcurrent leakage, and that preferably do not require high temperatureannealing, do not utilize oxidizers that can cause the formation of SiO₂interfacial layers on polysilicon substrates, and do not requirespecialized processing or substrate considerations.

SUMMARY OF THE INVENTION

The present invention is directed toward using a vapor depositionprocess using refractory metal precursor compounds and ethers to formrefractory metal oxide layers, especially tantalum pentoxide (Ta₂O₅)layers, on substrates. The vapor deposition process is preferably areactive vapor deposition process that involves co-reacting theprecursor compounds and the ethers.

The methods of the present invention involve forming a refractory metaloxide layer on a substrate by using a vapor deposition process and oneor more refractory metal precursor compounds of the formula MY_(n)(Formula I), wherein M is a refractory metal, each Y is independently ahalogen atom, and n is an integer selected to match the valence of themetal M, and one or more ethers of the formula R¹—O—R², wherein R¹ andR² are each independently organic groups.

In one embodiment, a method of forming a layer on a substrate isprovided that includes: providing a substrate (preferably asemiconductor substrate or substrate assembly such as a silicon wafer);providing a vapor that includes one or more refractory metal precursorcompounds of the formula MY_(n), wherein M is a refractory metal (e.g.,tantalum), each Y is independently a halogen atom (preferably, F, Cl, I,or combinations thereof, and more preferably, F), and n is an integerselected to match the valence of the metal M (e.g., n=5 when M=Ta);providing a vapor that includes one or more ethers of the formulaR¹—O—R², wherein R¹ and R² are each independently organic groups (e.g.,alkyl groups, alkenyl groups, aryl groups, silyl groups, andcombinations thereof); and directing the vapors of the one or morerefractory metal precursor compounds and the one or more ethers to thesubstrate to form a refractory metal oxide layer on one or more surfacesof the substrate.

The present invention also provides a method of manufacturing a memorydevice. The method includes: providing a substrate (preferably asemiconductor substrate or substrate assembly such as a silicon wafer)having a first electrode thereon; providing a vapor that includes one ormore refractory metal precursor compounds of the formula MY_(n), whereinM is a refractory metal, each Y is independently a halogen atom, and nis an integer selected to match the valence of the metal M; providing avapor that includes one or more ethers of the formula R¹—O—R², whereinR¹ and R² are each independently organic groups; directing the vaporsthat include the one or more refractory metal precursor compounds andthe one or more ethers to the substrate to form a refractory metal oxidedielectric layer on the first electrode of the substrate; and forming asecond electrode on the dielectric layer.

The present invention also provides a vapor deposition apparatus thatincludes: a vapor deposition chamber having a substrate (e.g., a siliconwafer) positioned therein; and one or more vessels that include one ormore refractory metal precursor compounds of the formula MY_(n), whereinM is a refractory metal, each Y is independently a halogen atom, and nis an integer selected to match the valence of the metal M; and one ormore vessels that include one or more ethers of the formula R¹—O—R²,wherein R¹ and R² are each independently organic groups. Optionally, theapparatus includes one or more sources of an inert carrier gas fortransferring the precursors to the vapor deposition chamber, and/or oneor more vessels that include one or more metal-containing precursorcompounds having a formula different from MY_(n).

The methods of the present invention can utilize a chemical vapordeposition (CVD) process, which can be pulsed, or an atomic layerdeposition (ALD) process (a self-limiting vapor deposition process thatincludes a plurality of deposition cycles, typically with purgingbetween the cycles). Preferably, the methods of the present inventionuse ALD. For certain ALD processes, the tantalum oxide layer is formedby alternately introducing one or more precursor compounds and ethersinto a deposition chamber during each deposition cycle.

“Substrate” as used herein refers to any base material or constructionupon which a metal-containing layer can be deposited. The term“substrate” is meant to include semiconductor substrates and alsoinclude non-semiconductor substrates such as films, molded articles,fibers, wires, glass, ceramics, machined metal parts, etc.“Semiconductor substrate” or “substrate assembly” as used herein refersto a semiconductor substrate such as a metal electrode, basesemiconductor layer or a semiconductor substrate having one or morelayers, structures, or regions formed thereon. A base semiconductorlayer is typically the lowest layer of silicon material on a wafer or asilicon layer deposited on another material, such as silicon onsapphire. When reference is made to a substrate assembly, variousprocess steps may have been previously used to form or define regions,junctions, various structures or features, and openings such ascapacitor plates or barriers for capacitors.

“Layer” as used herein refers to any metal-containing layer that can beformed on a substrate from the precursor compounds of this inventionusing a vapor deposition process. The term “layer” is meant to includelayers specific to the semiconductor industry, such as “barrier layer,”“dielectric layer,” and “conductive layer.” (The term “layer” issynonymous with the term “film” frequently used in the semiconductorindustry.) The term “layer” is also meant to include layers found intechnology outside of semiconductor technology, such as coatings onglass.

“Dielectric layer” as used herein is a term used in the semiconductorindustry that refers to an insulating layer (sometimes referred to as a“film”) having a high dielectric constant that is typically positionedbetween two conductive electrodes to form a capacitor. For thisinvention, the dielectric layer is a refractory metal oxide layer,preferably a Ta₂O₅ layer, formed using a reactive deposition process.

“Refractory metal” as defined by Webster's New Universal UnabridgedDictionary (1992) is a metal that is difficult to fuse, reduce, or work.For the purposes of this invention, the term “refractory metal” is meantto include the Group IVB metals (i.e., titanium (Ti), zirconium (Zr),hafnium (Hf)); the Group VB metals (i.e., vanadium (V), niobium (Nb),tantalum (Ta)); and the Group VIB metals (i.e., chromium (Cr),molybdenum (Mo) and tungsten (W)).

“Precursor compound” as used herein refers to refractory metal precursorcompounds, tantalum precursor compounds, nitrogen precursor compounds,silicon precursor compounds, and other metal-containing precursorcompounds, for example. A suitable precursor compound is one that iscapable of forming, either alone or with other precursor compounds, arefractory metal-containing layer on a substrate using a vapordeposition process. The resulting metal-containing layers are typicallyoxide layers, which are useful as dielectric layers.

“Deposition process” and “vapor deposition process” as used herein referto a process in which a metal-containing layer is formed on one or moresurfaces of a substrate (e.g., a doped polysilicon wafer) from vaporizedprecursor compound(s). Specifically, one or more metal precursorcompounds are vaporized and directed to one or more surfaces of a heatedsubstrate (e.g., semiconductor substrate or substrate assembly) placedin a deposition chamber. These precursor compounds form (e.g., byreacting or decomposing) a non-volatile, thin, uniform, metal-containinglayer on the surface(s) of the substrate. For the purposes of thisinvention, the term “vapor deposition process” is meant to include bothchemical vapor deposition processes (including pulsed chemical vapordeposition processes) and atomic layer deposition processes.

“Chemical vapor deposition” (CVD) as used herein refers to a vapordeposition process wherein the desired layer is deposited on thesubstrate from vaporized metal precursor compounds and any reactiongases used within a deposition chamber with no effort made to separatethe reaction components. In contrast to a “simple” CVD process thatinvolves the substantial simultaneous use of the precursor compounds andany reaction gases, “pulsed” CVD alternately pulses these materials intothe deposition chamber, but does not rigorously avoid intermixing of theprecursor and reaction gas streams, as is typically done in atomic layerdeposition or ALD (discussed in greater detail below).

“Atomic layer deposition” (ALD) as used herein refers to a vapordeposition process in which numerous consecutive deposition cycles areconducted in a deposition chamber. Typically, during each cycle themetal precursor is chemisorbed to the substrate surface; excessprecursor is purged out; a subsequent precursor and/or reaction gas isintroduced to react with the chemisorbed layer; and excess reaction gas(if used) and by-products are removed. As compared to the one cyclechemical vapor deposition (CVD) process, the longer duration multi-cycleALD process allows for improved control of layer thickness byself-limiting layer growth and minimizing detrimental gas phasereactions by separation of the reaction components. The term “atomiclayer deposition” as used herein is also meant to include the relatedterms “atomic layer epitaxy” (ALE) (see U.S. Pat. No. 5,256,244(Ackerman)), molecular beam epitaxy (MBE), gas source MBE,organometallic MBE, and chemical beam epitaxy when performed withalternating pulses of precursor compound(s), reaction gas and purge(i.e., inert carrier) gas.

“Chemisorption” as used herein refers to the chemical adsorption ofvaporized reactive precursor compounds on the surface of a substrate.The adsorbed species are irreversibly bound to the substrate surface asa result of relatively strong binding forces characterized by highadsorption energies (>30 kcal/mol), comparable in strength to ordinarychemical bonds. The chemisorbed species are limited to the formation ofa monolayer on the substrate surface. (See “The Condensed ChemicalDictionary”, 10th edition, revised by G. G. Hawley, published by VanNostrand Reinhold Co., New York, 225 (1981)). The technique of ALD isbased on the principle of the formation of a saturated monolayer ofreactive precursor molecules by chemi sorption. In ALD one or moreappropriate reactive precursor compounds are alternately introduced(e.g., pulsed) into a deposition chamber and chemisorbed onto thesurfaces of a substrate. Each sequential introduction of a reactiveprecursor compound is typically separated by an inert carrier gas purge.Each precursor compound co-reaction adds a new atomic layer topreviously deposited layers to form a cumulative solid layer. The cycleis repeated, typically for several hundred times, to gradually form thedesired layer thickness. It should be understood, however, that ALD canuse one precursor compound and one reaction gas.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-3 are exemplary capacitor constructions.

FIG. 4 is a perspective view of a vapor deposition coating systemsuitable for use in the method of the present invention.

DETALED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

The present invention provides a method of forming metal oxide layers onsubstrates by using vapor deposition processes using one or morerefractory metal precursor compounds and one or more ethers. Therefractory metal precursor compounds are of the formula MY_(n), whereinM is a refractory metal, each Y is independently a halogen atom, and nis an integer selected to match the valence of the metal M. The one ormore ethers are of the formula R¹—O—R², wherein R¹ and R² are eachindependently organic groups. Preferably, M is tantalum and the formedrefractory metal oxide layer is a tantalum pentoxide layer.

The layers or films formed can be in the form of refractory metaloxide-containing films, wherein the layer includes one or morerefractory metal oxides optionally doped with other metals. Thus, theterm “refractory metal oxide” films or layers encompass just refractorymetal oxide as well as doped films or layers thereof (i.e., mixed metaloxides). Such mixed metal species can be formed using one or moremetal-containing precursor compounds of a formula different from FormulaI, which can be readily determined by one of skill in the art.

The refractory metal oxide layers typically have a thickness of about 10Å to about 100 Å. A preferred layer is a Ta₂O₅ layer. Preferred tantalumpentoxide layers include a combination of amorphous material and atleast some crystalline hexagonal phase, preferably with patterned (001)orientation. Such Ta₂O₅ layers do not require high temperature annealing(i.e., heating to temperatures of at least 700° C.) as is normallyrequired to crystallize fully amorphous layers but surprisingly exhibita desirable combination of high dielectric constants, typically in therange of 50 to 100, and low leakage currents, typically in the range of10⁻⁷ to 10⁻⁹ A/cm², soon after completion of the vapor depositionprocessing.

The substrate on which the metal-containing layer is formed ispreferably a semiconductor substrate or substrate assembly. Any suitablesemiconductor material is contemplated, such as for example,conductively doped polysilicon (for this invention simply referred to as“silicon”). A substrate assembly may also contain a layer that includesplatinum, iridium, rhodium, ruthenium, ruthenium oxide, titaniumnitride, tantalum nitride, tantalum-silicon-nitride, silicon dioxide,aluminum, gallium arsenide, glass, etc., and other existing orto-be-developed materials used in semiconductor constructions, such asdynamic random access memory (DRAM) devices and static random accessmemory (SRAM) devices, for example.

Substrates other than semiconductor substrates or substrate assembliescan be used in methods of the present invention. These include, forexample, fibers, wires, etc. If the substrate is a semiconductorsubstrate or substrate assembly, the layers can be formed directly onthe lowest semiconductor surface of the substrate, or they can be formedon any of a variety of the layers (i.e., surfaces) as in a patternedwafer, for example.

Refractory metal precursor compounds useful in the practice of thisinvention include any reactive refractory metal compounds. Preferably,the refractory metal precursor compounds are of the formula MY_(n)(Formula I), wherein M is a refractory metal, Y is independently ahalogen atom, and n is an integer selected to match the valence of themetal M (e.g., n would be 5 for a pentavalent metal). More preferably,each Y is a fluorine atom. More preferably, M is Ti, Nb, Ta, Mo, or W.Most preferably, M is Ti or Ta.

Preferably, M is tantalum and n is 5, so that the refractory metalprecursor compound is a tantalum precursor compound of the formula TaY₅wherein Y is defined as above. More preferably, Y is fluorine and thetantalum precursor compound is TaF₅. Useful tantalum precursor compoundsinclude TaF₅, TaCl₅, and TaBr₅ (all available from Sigma-AldrichChemical Company, Milwaukee, Wis.).

Ether compounds useful in this invention are of the formula R¹—O—R²wherein R¹ and R² is each independently an organic group. As usedherein, the term “organic group” is used for the purpose of thisinvention to mean a hydrocarbon group that is classified as an aliphaticgroup, cyclic group, or combination of aliphatic and cyclic groups(e.g., alkaryl and aralkyl groups). In the context of the presentinvention, suitable organic groups for precursor compounds of thisinvention are those that do not interfere with the formation of ametal-containing layer using vapor deposition techniques. In the contextof the present invention, the term “aliphatic group” means a saturatedor unsaturated linear or branched hydrocarbon group. This term is usedto encompass alkyl, alkenyl, and alkynyl groups, for example. The term“alkyl group” means a saturated linear or branched monovalenthydrocarbon group including, for example, methyl, ethyl, n-propyl,isopropyl, t-butyl, amyl, heptyl, 2-ethylhexyl, dodecyl, octadecyl, andthe like. The term “alkenyl group” means an unsaturated, linear orbranched monovalent hydrocarbon group with one or more olefinicallyunsaturated groups (i.e., carbon-carbon double bonds), such as a vinylgroup. The term “alkynyl group” means an unsaturated, linear or branchedmonovalent hydrocarbon group with one or more carbon-carbon triplebonds. The term “cyclic group” means a closed ring hydrocarbon groupthat is classified as an alicyclic group, aromatic group, orheterocyclic group. The term “alicyclic group” means a cyclichydrocarbon group having properties resembling those of aliphaticgroups. The term “aromatic group” or “aryl group” means a mono- orpolynuclear aromatic hydrocarbon group. The term “heterocyclic group”means a closed ring hydrocarbon in which one or more of the atoms in thering is an element other than carbon (e.g., nitrogen, oxygen, sulfur,etc.).

As a means of simplifying the discussion and the recitation of certainterminology used throughout this application, the terms “group” and“moiety” are used to differentiate between chemical species that allowfor substitution or that may be substituted and those that do not soallow for substitution or may not be so substituted. Thus, when the term“group” is used to describe a chemical substituent, the describedchemical material includes the unsubstituted group and that group withnonperoxidic O, N, S, Si, or F, atoms, for example, in the chain as wellas carbonyl groups or other conventional substituents. Where the term“moiety” is used to describe a chemical compound or substituent, only anunsubstituted chemical material is intended to be included. For example,the phrase “alkyl group” is intended to include not only pure open chainsaturated hydrocarbon alkyl substituents, such as methyl, ethyl, propyl,t-butyl, and the like, but also alkyl substituents bearing furthersubstituents known in the art, such as hydroxy, alkoxy, alkylsulfonyl,halogen atoms, cyano, nitro, amino, carboxyl, etc. Thus, “alkyl group”includes ether groups, haloalkyls, nitroalkyls, carboxyalkyls,hydroxyalkyls, sulfoalkyls, etc. On the other hand, the phrase “alkylmoiety” is limited to the inclusion of only pure open chain saturatedhydrocarbon alkyl substituents, such as methyl, ethyl, propyl, t-butyl,and the like.

In the ether compounds, preferably at least one of R¹ and R² is selectedfrom the group of alkyl groups, alkenyl groups, aryl groups, silylgroups, or combinations thereof (any of which may be branched orunbranched). At least one of R¹ and R² can optionally contain functionalgroups such as ether, amino, and carbonyl groups. More preferably, atleast one of R¹ and R² is an alkyl, alkenyl, aryl, or silyl group(preferably an alkyl group) that forms a stable radical or carbocation,such as a benzyl, allyl, t-butyl, dimethylsilyl or trimethylsilyl group.Most preferably, at least one of R¹ and R² is a group also capable ofabstracting halide groups from MY_(n). Examples of suchhalide-abstracting groups are dimethylsilyl and trimethylsilyl groups.Examples of useful ether compounds include (CH₃)₃Si—O—Si(CH₃)₃(1,1,1,3,3,3-hexamethyldisiloxane), (CH₃)₂(H)Si—O—Si(H)(CH₃)₂(1,1,3,3-tetramethyldisiloxane), (CH₃)₃C—O—C(CH₃)₃ (di-tert-butyl ether)and C₆H₅CH₂—O—CH₂C₆H₅ (dibenzyl ether).

Various precursor compounds can be used in various combinations,optionally with one or more organic solvents (particularly for CVDprocesses), to form a precursor composition. The precursor compounds maybe liquids or solids at room temperature (preferably, they are liquidsat the vaporization temperature). Typically, they are liquidssufficiently volatile to be employed using known vapor depositiontechniques. However, as solids they may also be sufficiently volatilethat they can be vaporized or sublimed from the solid state using knownvapor deposition techniques. If they are less volatile solids, they arepreferably sufficiently soluble in an organic solvent or have meltingpoints below their decomposition temperatures such that they can be usedin flash vaporization, bubbling, microdroplet formation techniques, etc.Herein, vaporized precursor compounds may be used either alone oroptionally with vaporized molecules of other precursor compounds oroptionally with vaporized solvent molecules, if used. As used herein,“liquid” refers to a solution or a neat liquid (a liquid at roomtemperature or a solid at room temperature that melts at an elevatedtemperature). As used herein, “solution” does not require completesolubility of the solid but may allow for some undissolved solid, aslong as there is a sufficient amount of the solid delivered by theorganic solvent into the vapor phase for chemical vapor depositionprocessing. If solvent dilution is used in deposition, the total molarconcentration of solvent vapor generated may also be considered as ainert carrier gas.

The solvents that are suitable for this application (particularly for aCVD process) can be one or more of the following: aliphatic hydrocarbonsor unsaturated hydrocarbons (C3-C20, and preferably C5-C10, cyclic,branched, or linear), aromatic hydrocarbons (C5-C20, and preferablyC5-C10), halogenated hydrocarbons, silylated hydrocarbons such asalkylsilanes, alkylsilicates, ethers, polyethers, thioethers, esters,lactones, ammonia, amides, amines (aliphatic or aromatic, primary,secondary, or tertiary), polyamines, nitriles, cyanates, isocyanates,thiocyanates, silicone oils, alcohols, or compounds containingcombinations of any of the above or mixtures of one or more of theabove. The compounds are also generally compatible with each other, sothat mixtures of variable quantities of the precursor compounds will notinteract to significantly change their physical properties.

The precursor compounds can be vaporized in the presence of an inertcarrier gas if desired. Additionally, an inert carrier gas can be usedin purging steps in an ALD process. The inert carrier gas is typicallyselected from the group consisting of nitrogen, helium, argon, andmixtures thereof. In the context of the present invention, an inertcarrier gas is one that is generally unreactive with the complexesdescribed herein and does not interfere with the formation of thedesired metal-containing film (i.e., layer).

The deposition process for this invention is a vapor deposition process.Vapor deposition processes are generally favored in the semiconductorindustry due to the process capability to quickly provide highlyconformal layers even within deep contacts and other openings. Chemicalvapor deposition (CVD) and atomic layer deposition (ALD) are two vapordeposition processes often employed to form thin, continuous, uniform,metal-containing (preferably dielectric) layers onto semiconductorsubstrates. Using either vapor deposition process, typically one or moreprecursor compounds are vaporized in a deposition chamber and optionallycombined with one or more reaction gases to form a metal-containinglayer onto a substrate. It will be readily apparent to one skilled inthe art that the vapor deposition process may be enhanced by employingvarious related techniques such as plasma assistance, photo assistance,laser assistance, as well as other techniques.

The final layer (preferably, a dielectric layer) formed preferably has athickness in the range of about 10 Å to about 500 Å. More preferably,the thickness of the metal-containing layer is in the range of about 30Å to about 80 Å.

In most vapor deposition processes, the precursor compound(s) aretypically reacted with an oxidizing or reducing reaction gas at elevatedtemperatures to form the refractory metal-containing layer. However, inthe practice of this invention, no such reaction gas is needed as theether provides the source of oxygen needed in the vapor depositionprocess when reacting with the refractory metal precursor compound(s) toform the refractory metal-containing layer.

Chemical vapor deposition (CVD) has been extensively used for thepreparation of metal-containing layers, such as dielectric layers, insemiconductor processing because of its ability to provide highlyconformal and high quality dielectric layers at relatively fastprocessing times. The desired precursor compounds are vaporized and thenintroduced into a deposition chamber containing a heated substrate withoptional reaction gases and/or inert carrier gases. In a typical CVDprocess, vaporized precursors are contacted with reaction gas(es) at thesubstrate surface to form a layer (e.g., dielectric layer). The singledeposition cycle is allowed to continue until the desired thickness ofthe layer is achieved.

Typical CVD processes generally employ precursor compounds invaporization chambers that are separated from the process chamberwherein the deposition surface or wafer is located. For example, liquidprecursor compounds are typically placed in bubblers and heated to atemperature at which they vaporize, and the vaporized liquid precursorcompound is then transported by an inert carrier gas passing over thebubbler or through the liquid precursor compound. The vapors are thenswept through a gas line to the deposition chamber for depositing alayer on substrate surface(s) therein. Many techniques have beendeveloped to precisely control this process. For example, the amount ofprecursor material transported to the deposition chamber can beprecisely controlled by the temperature of the reservoir containing theprecursor compounds and by the flow of an inert carrier gas bubbledthrough or passed over the reservoir.

Preferred embodiments of the precursor compounds described herein areparticularly suitable for chemical vapor deposition (CVD). Thedeposition temperature at the substrate surface is preferably held at atemperature in a range of about 100° C. to about 600° C., morepreferably in the range of about 200° C. to about 500° C. The depositionchamber pressure is preferably maintained at a deposition pressure ofabout 0.1 torr to about 10 torr. The partial pressure of precursorcompounds in the inert carrier gas is preferably about 0.001 torr toabout 10 torr.

Several modifications of the CVD process and chambers are possible, forexample, using atmospheric pressure chemical vapor deposition, lowpressure chemical vapor deposition (LPCVD), plasma enhanced chemicalvapor deposition (PECVD), hot wall or cold wall reactors or any otherchemical vapor deposition technique. Furthermore, pulsed CVD can beused, which is similar to ALD (discussed in greater detail below) butdoes not rigorously avoid intermixing of percursor and reactant gasstreams. Also, for pulsed CVD, the deposition thickness is dependent onthe exposure time, as opposed to ALD, which is self-limiting (discussedin greater detail below).

A typical CVD process may be carried out in a chemical vapor depositionreactor, such as a deposition chamber available under the tradedesignation of 7000 from Genus, Inc. (Sunnyvale, Calif.), a depositionchamber available under the trade designation of 5000 from AppliedMaterials, Inc. (Santa Clara, Calif.), or a deposition chamber availableunder the trade designation of Prism from Novelus, Inc. (San Jose,Calif.). However, any deposition chamber suitable for performing CVD maybe used.

Alternatively, and preferably, the vapor deposition process employed inthe methods of the present invention is a multi-cycle ALD process. Sucha process is advantageous (particularly over a CVD process) in that inprovides for optimum control of atomic-level thickness and uniformity tothe deposited layer (e.g., dielectric layer) and to expose the metalprecursor compounds to lower volatilization and reaction temperatures tominimize degradation. Typically, in an ALD process, each reactant ispulsed sequentially onto a suitable substrate, typically at depositiontemperatures of about 25° C. to about 400° C. (preferably about 150° C.to about 300° C.), which is generally lower than presently used in CVDprocesses. Under such conditions the film growth is typicallyself-limiting (i.e., when the reactive sites on a surface are used up inan ALD process, the deposition generally stops), insuring not onlyexcellent conformality but also good large area uniformity plus simpleand accurate thickness control. Due to alternate dosing of the precursorcompounds and/or reaction gases, detrimental vapor-phase reactions areinherently eliminated, in contrast to the CVD process that is carriedout by continuous coreaction of the precursors and/or reaction gases.(See Vehkamaki et al, “Growth of SrTiO₃ and BaTiO₃ Thin Films by AtomicLayer Deposition,” Electrochemical and Solid-State Letters,2(10):504-506 (1999)).

A typical ALD process includes exposing an initial substrate to a firstchemical species (e.g., refractory metal precursor compound of theformula MY_(n)) to accomplish chemisorption of the species onto thesubstrate. Theoretically, the chemisorption forms a monolayer that isuniformly one atom or molecule thick on the entire exposed initialsubstrate. In other words, a saturated monolayer. Practically,chemisorption might not occur on all portions of the substrate.Nevertheless, such an imperfect monolayer is still a monolayer in thecontext of the present invention. In many applications, merely asubstantially saturated monolayer may be suitable. A substantiallysaturated monolayer is one that will still yield a deposited layerexhibiting the quality and/or properties desired for such layer.

The first species is purged from over the substrate and a secondchemical species (e.g., a different compound of the formula MY_(n), ametal-containing precursor compound or a formula different than MY_(n),or an ether compound) is provided to react with the first monolayer ofthe first species. The second species is then purged and the steps arerepeated with exposure of the second species monolayer to the firstspecies. In some cases, the two monolayers may be of the same species.As an option, the second species can react with the first species, butnot chemisorb additional material thereto. That is, the second speciescan cleave some portion of the chemisorbed first species, altering suchmonolayer without forming another monolayer thereon. Also, a thirdspecies or more may be successively chemisorbed (or reacted) and purgedjust as described for the first and second species.

Purging may involve a variety of techniques including, but not limitedto, contacting the substrate and/or monolayer with a carrier gas and/orlowering pressure to below the deposition pressure to reduce theconcentration of a species contacting the substrate and/or chemisorbedspecies. Examples of carrier gases include N₂, Ar, He, etc. Purging mayinstead include contacting the substrate and/or monolayer with anysubstance that allows chemisorption by-products to desorb and reducesthe concentration of a contacting species preparatory to introducinganother species. The contacting species may be reduced to some suitableconcentration or partial pressure known to those skilled in the artbased on the specifications for the product of a particular depositionprocess.

ALD is often described as a self-limiting process, in that a finitenumber of sites exist on a substrate to which the first species may formchemical bonds. The second species might only bond to the first speciesand thus may also be self-limiting. Once all of the finite number ofsites on a substrate are bonded with a first species, the first specieswill often not bond to other of the first species already bonded withthe substrate. However, process conditions can be varied in ALD topromote such bonding and render ALD not self-limiting. Accordingly, ALDmay also encompass a species forming other than one monolayer at a timeby stacking of a species, forming a layer more than one atom or moleculethick.

The described method indicates the “substantial absence” of the secondprecursor (i.e., second species) during chemisorption of the firstprecursor since insignificant amounts of the second precursor might bepresent. According to the knowledge and the preferences of those withordinary skill in the art, a determination can be made as to thetolerable amount of second precursor and process conditions selected toachieve the substantial absence of the second precursor.

Thus, during the ALD process, numerous consecutive deposition cycles areconducted in the deposition chamber, each cycle depositing a very thinmetal-containing layer (usually less than one monolayer such that thegrowth rate on average is from about 0.2 to about 3.0 Angstroms percycle), until a layer of the desired thickness is built up on thesubstrate of interest. The layer deposition is accomplished byalternately introducing (i.e., by pulsing) refractory metal precursorcompound(s) and ether compound(s) into the deposition chamber containinga semiconductor substrate, chemisorbing the precursor compound(s) as amonolayer onto the substrate surfaces, and then reacting the chemisorbedprecursor compound(s) with the other co-reactive precursor compound(s).The pulse duration of precursor compound(s) and inert carrier gas(es) issufficient to saturate the substrate surface. Typically, the pulseduration is from about 0.1 to about 5 seconds, preferably from about 0.2to about 1 second.

In comparison to the predominantly thermally driven CVD, ALD ispredominantly chemically driven. Accordingly, ALD is often conducted atmuch lower temperatures than CVD. During the ALD process, the substratetemperature is maintained at a temperature sufficiently low to maintainintact bonds between the cherisorbed precursor compound(s) and theunderlying substrate surface and to prevent decomposition of theprecursor compound(s). The temperature is also sufficiently high toavoid condensation of the precursor compounds(s). Typically thesubstrate temperature is kept within the range of about 25° C. to about400° C. (preferably about 150° C. to about 300° C.), which is generallylower than presently used in CVD processes. Thus, the first species orprecursor compound is chemisorbed at this temperature. Surface reactionof the second species or precursor compound can occur at substantiallythe same temperature as chemisorption of the first precursor or, lesspreferably, at a substantially different temperature. Clearly, somesmall variation in temperature, as judged by those of ordinary skill,can occur but still be a substantially same temperature by providing areaction rate statistically the same as would occur at the temperatureof the first precursor chemisorption. Chemisorption and subsequentreactions could instead occur at exactly the same temperature.

For a typical ALD process, the pressure inside the deposition chamber iskept at about 10⁻⁴ torr to about 1 torr, preferably about 10⁻⁴ torr toabout 0.1 torr. Typically, the deposition chamber is purged with aninert carrier gas after the vaporized precursor compound(s) have beenintroduced into the chamber and/or reacted for each cycle. The inertcarrier gas(es) can also be introduced with the vaporized precursorcompound(s) during each cycle.

The reactivity of a precursor compound can significantly influence theprocess parameters in ALD. Under typical CVD process conditions, ahighly reactive compound may react in the gas phase generatingparticulates, depositing prematurely on undesired surfaces, producingpoor films, and/or yielding poor step coverage or otherwise yieldingnon-uniform deposition. For at least such reason, a highly reactivecompound might be considered not suitable for CVD. However, somecompounds not suitable for CVD are superior ALD precursors. For example,if the first precursor is gas phase reactive with the second precursor,such a combination of compounds might not be suitable for CVD, althoughthey could be used in ALD. In the CVD context, concern might also existregarding sticking coefficients and surface mobility, as known to thoseskilled in the art, when using highly gas-phase reactive precursors,however, little or no such concern would exist in the ALD context.

After layer formation on the substrate, an annealing process can beoptionally performed in situ in the deposition chamber in a nitrogenatmosphere or oxidizing atmosphere. Preferably, the annealingtemperature is within the range of about 400° C. to about 1000° C.Particularly after ALD, the annealing temperature is more preferablyabout 400° C. to about 750° C., and most preferably about 600° C. toabout 700° C. The annealing operation is preferably performed for a timeperiod of about 0.5 minute to about 60 minutes and more preferably for atime period of about 1 minute to about 10 minutes. One skilled in theart will recognize that such temperatures and time periods may vary. Forexample, furnace anneals and rapid thermal annealing may be used, andfurther, such anneals may be performed in one or more annealing steps.

As stated above, the use of the complexes and methods of forming filmsof the present invention are beneficial for a wide variety of thin filmapplications in semiconductor structures, particularly those using highdielectric materials or ferroelectric materials. For example, suchapplications include capacitors such as planar cells, trench cells(e.g., double sidewall trench capacitors), stacked cells (e.g., crown,V-cell, delta cell, multi-fingered, or cylindrical container stackedcapacitors), as well as field effect transistor devices.

A specific example of where a dielectric layer is formed according tothe present invention is a capacitor construction. Exemplary capacitorconstructions are described with reference to FIGS. 1-3. Referring toFIG. 1, a semiconductor wafer fragment 10 includes a capacitorconstruction 25 formed by a method of the present invention. Waferfragment 10 includes a substrate 12 having a conductive diffusion area14 formed therein. Substrate 12 can include, for example,monocrystalline silicon. An insulating layer 16, typicallyborophosphosilicate glass (BPSG), is provided over substrate 12, with acontact opening 18 provided therein to diffusion area 14. A conductivematerial 20 fills contact opening 18, with material 20 and oxide layer18 having been planarized as shown. Material 20 might be any suitableconductive material, such as, for example, tungsten or conductivelydoped polysilicon. Capacitor construction 25 is provided atop layer 16and plug 20, and electrically connected to node 14 through plug 20.

Capacitor construction 25 includes a first capacitor electrode 26, whichhas been provided and patterned over node 20. Examplary materialsinclude conductively doped polysilicon, Pt, Ir, Rh, Ru, RuO₂, IrO₂,RhO₂. A capacitor dielectric layer 28 is provided over first capacitorelectrode 26. The materials of the present invention can be used to formthe capacitor dielectric layer 28. Preferably, if first capacitorelectrode 26 includes polysilicon, a surface of the polysilicon iscleaned by an in situ HF dip prior to deposition of the dielectricmaterial. An exemplary thickness for layer 28 in accordance with 256 Mbintegration is 100 Angstroms.

A diffusion barrier layer 30 is provided over dielectric layer 28.Diffusion barrier layer 30 includes conductive materials such as TiN,TaN, metal silicide, or metal silicide-nitride, and can be provided byCVD, for example, using conditions well known to those of skill in theart. After formation of barrier layer 30, a second capacitor electrode32 is formed over barrier layer 30 to complete construction of capacitor25. Second capacitor electrode 32 can include constructions similar tothose discussed above regarding the first capacitor electrode 26, andcan accordingly include, for example, conductively doped polysilicon.Diffusion barrier layer 30 preferably prevents components (e.g., oxygen)from diffusing from dielectric material 28 into electrode 32. If, forexample, oxygen diffuses into a silicon-containing electrode 32, it canundesirably form SiO₂, which will significantly reduce the capacitanceof capacitor 25. Diffusion barrier layer 30 can also prevent diffusionof silicon from metal electrode 32 to dielectric layer 28.

FIG. 2 illustrates an alternative embodiment of a capacitorconstruction. Like numerals from FIG. 1 have been utilized whereappropriate, with differences indicated by the suffix “a”. Waferfragment 10 a includes a capacitor construction 25 a differing from theconstruction 25 of FIG. 2 in provision of a barrier layer 30 a betweenfirst electrode 26 and dielectric layer 28, rather than betweendielectric layer 28 and second capacitor electrode 32. Barrier layer 30a can include constructions identical to those discussed above withreference to FIG. 1.

FIG. 3 illustrates yet another alternative embodiment of a capacitorconstruction. Like numerals from FIG. 1 are utilized where appropriate,with differences being indicated by the suffix “b” or by differentnumerals. Wafer fragment 10 b includes a capacitor construction 25 bhaving the first and second capacitor plate 26 and 32, respectively, ofthe first described embodiment. However, wafer fragment 10 b differsfrom wafer fragment 10 of FIG. 2 in that wafer fragment 10 b includes asecond barrier layer 40 in addition to the barrier layer 30. Barrierlayer 40 is provided between first capacitor electrode 26 and dielectriclayer 28, whereas barrier layer 30 is between second capacitor electrode32 and dielectric layer 28. Barrier layer 40 can be formed by methodsidentical to those discussed above with reference to FIG. 1 forformation of the barrier layer 30.

In the embodiments of FIGS. 1-3, the barrier layers are shown anddescribed as being distinct layers separate from the capacitorelectrodes. It is to be understood, however, that the barrier layers caninclude conductive materials and can accordingly, in such embodiments,be understood to include at least a portion of the capacitorrelectrodes. In particular embodiments an entirety of a capacitorelectrode can include conductive barrier layer materials.

A system that can be used to perform vapor deposition processes(chemical vapor deposition or atomic layer deposition) of the presentinvention is shown in FIG. 4. The system includes an enclosed vapordeposition chamber 110, in which a vacuum may be created using turbopump 112 and backing pump 114. One or more substrates 116 (e.g.,semiconductor substrates or substrate assemblies) are positioned inchamber 110. A constant nominal temperature is established for substrate116, which can vary depending on the process used. Substrate 116 may beheated, for example, by an electrical resistance heater 118 on whichsubstrate 116 is mounted. Other known methods of heating the substratemay also be utilized.

In this process, precursor compounds 160 (e.g., a refractory metalprecursor compound and an ether) are stored in vessels 162. Theprecursor compounds are vaporized and separately fed along lines 164 and166 to the deposition chamber 110 using, for example, an inert carriergas 168. A reaction gas 170 may be supplied along line 172 as needed.Also, a purge gas 174, which is often the same as the inert carrier gas168, may be supplied along line 176 as needed. As shown, a series ofvalves 180-185 are opened and closed as required.

The following examples are offered to further illustrate the variousspecific and preferred embodiments and techniques. It should beunderstood, however, that many variations and modifications may be madewhile remaining within the scope of the present invention, so the scopeof the invention is not intended to be limited by the examples.

EXAMPLES Example 1 Atomic Layer Deposition of Tantalum Pentoxide

Using an ALD process, precursor compounds tantalum pentafluoride,(TaF5), and 1,1,3,3-tetramethyldisiloxane, (CH₃)₂(H)Si—O—Si(H)(CH₃)₂,(both available from Sigma-Aldrich Chemical Co., Milwaukee, Wis.) werealternatively pulsed into a deposition chamber containing a platinumelectrode having a surface temperature of about 260° C. After 800cycles, a Ta₂O₅ layer having a thickness of 400 Å was achieved, thelayer having no silicon or carbon contamination and a only trace offluorine contamination (no more than 2 atom %) as determined by atomicemission spectroscopy (AES) analysis. X-ray diffraction analysis (XDA)showed the layer to be mainly amorphous with some (001) orientedhexagonal phase present, which remained the preferred crystallineorientation after the layer was annealed at 750° C. in an oxygenatmosphere.

A capacitor was formed by using physical vapor deposition to sputterplatinum top electrodes through a hard mask on the as-deposited Ta₂O₅layer. Dielectric constants of near 60 were obtained on 0.4 mm²capacitors, measured at frequencies between 0.1 kHz and 100 kHz. Leakagewas 6×10⁻⁷ A/cm². Excellent step coverage was obtained on structuredwafers with containers having a 10:1 aspect ratio.

The complete disclosures of the patents, patent documents, andpublications cited herein are incorporated by reference in theirentirety as if each were individually incorporated. Variousmodifications and alterations to this invention will become apparent tothose skilled in the art without departing from the scope and spirit ofthis invention. It should be understood that this invention is notintended to be unduly limited by the illustrative embodiments andexamples set forth herein and that such examples and embodiments arepresented by way of example only with the scope of the inventionintended to be limited only by the claims set forth herein as follows.

1-52. (Canceled)
 53. A vapor deposition apparatus comprising: a vapordeposition chamber having a substrate positioned therein; and one ormore vessels comprising one or more refractory metal precursor compoundsof the formula MY_(n) (Formula I), wherein M is a refractory metal, eachY is independently a halogen atom, and n is an integer selected to matchthe valence of the metal M; and one or more vessels comprising one ormore ethers of the formula R¹—O—R², wherein R¹ and R² are eachindependently organic groups.
 54. The apparatus of claim 53 wherein thesubstrate is a silicon wafer.
 55. The apparatus of claim 53 furthercomprising one or more sources of an inert carrier gas for transferringthe precursors to the vapor deposition chamber.
 56. The apparatus ofclaim 53 further comprising one or more vessels comprising one or moremetal-containing precursor compounds having a formula different thanFormula I.
 57. A vapor deposition apparatus comprising: a vapordeposition chamber; and one or more vessels comprising one or morerefractory metal precursor compounds of the formula MY_(n) (Formula I),wherein M is a refractory metal, each Y is independently a halogen atom,and n is an integer selected to match the valence of the metal M; andone or more vessels comprising one or more ethers of the formulaR¹—O—R², wherein R¹ and R² are each independently organic groups. 58.The apparatus of claim 57 wherein M is tantalum and n is
 5. 59. Theapparatus of claim 57 wherein Y is independently selected from the groupconsisting of F, Cl, I, and combinations thereof.
 60. The apparatus ofclaim 59 wherein each Y is independently a fluorine atom.
 61. Theapparatus of claim 60 wherein M is tantalum and n is
 5. 62. Theapparatus of claim 57 wherein at least one of R¹ and R² is selected fromthe group consisting of alkyl groups, alkenyl groups, aryl groups, silylgroups, and combinations thereof.
 63. The apparatus of claim 57 whereinat least one of R¹ and R² contains one or more functional groupsselected from the group consisting of ether, amino, and carbonyl groups.64. The apparatus of claim 57 wherein at least one of R¹ and R² is analkyl group that forms a stable radical or carbocation.
 65. Theapparatus of claim 57 wherein at least one of R¹ and R² is selected fromthe group consisting of benzyl, t-butyl, dimethylsilyl, andtrimethylsilyl groups.
 66. The apparatus of claim 65 wherein at leastone of R¹ and R² is selected from the group consisting of dimethylsilyland trimethylsilyl groups.
 67. The apparatus of claim 57 furthercomprising one or more vessels comprising one or more metal-containingprecursor compounds having a formula different than Formula I.
 68. Theapparatus of claim 57 wherein R¹—O—R² is hexamethyldisiloxane.
 69. Theapparatus of claim 57 wherein R¹—O—R² is tetramethyldisiloxane.
 70. Avapor deposition apparatus comprising: a vapor deposition chamber; andone or more vessels comprising one or more refractory metal precursorcompounds of the formula MY_(n) (Formula I), wherein M is a refractorymetal, each Y is independently a halogen atom, and n is an integerselected to match the valence of the metal M; and one or more vesselscomprising one or more ethers of the formula R¹—O—R², wherein R¹ and R²are each independently organic groups, with the proviso that at leastone of the one or more ethers comprises tetramethyldisiloxane.
 71. Avapor deposition apparatus comprising: a vapor deposition chamber; andone or more vessels comprising one or more refractory metal precursorcompounds of the formula MY_(n) (Formula I), wherein M is a refractorymetal, each Y is independently a halogen atom, and n is an integerselected to match the valence of the metal M; and one or more vesselscomprising one or more ethers of the formula R¹—O—R², wherein R¹ and R²are each independently organic groups, with the proviso that the one ormore ethers do not comprise disilyl ethers.